A preposition For native English speaker , How do they use preposition ? Is it natural sense ? Tell me the image of preposition !!

A Bunch of nuts I follow glee-official on Instagram ,yesterday glee said "family is like fudge ,but with a bunch of Nuts" I couldnt understand "A bunch of nuts" I think ... A bunch of nuts means "confidential" Pls tell me the meaning of "a bunch of nuts"